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Insulation in Crawl Space - Foam or Rolls for DIY

Insulation in Crawl Space - Foam or Rolls for DIY

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  #1  
Old 11-11-11, 02:38 PM
J
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Insulation in Crawl Space - Foam or Rolls for DIY

Hello.

I recently pulled up my carpet and replaced them with hardwood floors in my family room and dining room. Now that itís colder, Iím seeing a noticeable difference in the temperature in that room compared to other rooms in the house. It goes so far as to feel a slight draft coming through near the edges/walls.

I went into the crawl space and noticed there was no insulation, simply an exposed sub-floor. I donít have much experience in insulation other than just putting in the pink rolls into walls, so the relatively obvious solution from a DIY perspective was to simply get some 24Ē rolls of crawl space insulation and hold it up with some twine/straps.

It isnít too complicated, but I do have three concerns that make me want to run it by folks. 1) The space is pretty tight in that I only have about 24Ē from the sub-floor to the plastic on the ground. So it will be a little back-breaking to shimmy on my stomach around there getting straps screwed in and running the rolls. 2) There are a number of pipes going through the beams just 2-3Ē off the sub-floor. So the rolls would have to be run over the top of these or something creative. 3) There arenít joists, simply beams running about every 4í or so, thus I would need to run two 24Ē insulation rolls side-by-side, which may not end up being too terribly difficult, but it seems like it could be a chore getting two side-by-side rolls running down a span and getting a strap to hold them both up perfectly.

Since insulation hasnít really been my area of expertise and I havenít read-up much on it in the last 20+ years, Iím wondering if they have some modern, easy DIY applications at my local box store for spray-on closed cell insulation that I can simply spray on there and easily access those hard to reach areas and not have to worry about hanging up straps and such. Iím OK buying the rolls and doing it if I have to, as I donít want to pay $500+ for a pro to come out and spray in some expensive material and charge for their labor and equipment when I could just get $200 in rolls and achieve the same result. But if I can just buy the material and applicator for about the same cost as the rolls, might make life easier to go that route.

Anyone with expertise in insulation that can give me some advice on a DIY novice in insulation doing one versus the other?

Thanks

Hereís a pic of the space.
Crawlspace001.jpg picture by jeffsinpdx - Photobucket
 
  #2  
Old 11-11-11, 04:13 PM
B
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Spray foam would be far from the same results or same costs. Hanging the insulation as you describe is a waste if money. The effective insulation value is nil and over time it gets worse.

Another approach is to insulate the perimeter if the crawl space, ground up to the bottom of the floor. This covers less area and minimizes the crawling around. It also protect any pipes down there. I'll attach a building science link which will bring you up to speed on crawl space issues:
BSI-009: New Light In Crawlspaces — Building Science Information

Bud
 
  #3  
Old 11-11-11, 05:16 PM
J
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I'll read that article when I have some time later this evening, it could clear up the questions.

I'm a little confused as to "insulating the perimeter". Do you mean the vertical foundation walls around the perimeter of the crawl space? They are simply 24" of concrete and have vents every six feet, so there is no way to do that without completely plugging the vents and taking away the ventalation to the crawl space. Or do you mean to simply spray foam insulation around the edge 6-12" of subfloor all around the edges? Not sure what direction you were going there.

After pondering it some more, I'm also wondering if some of those 2" thick 4'x8' poly rigid foam insulation boards might not fit well into my 4' span. Then I can just grab some cans of those $5/can foam spray cans and fill in the small inch gap left on the edges. That might also achieve the same thing without a large cost of spraying in foam all over the entire 500 sqft section of sub-floor I'm having to cover.
 
  #4  
Old 11-12-11, 07:10 AM
B
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Hi Jeff,
No wonder it's cold, those vents open and no insulation anywhere. If you have humid summers, those vents need to be closed in the summer. If you have cold winters, then again, those vents need to be closed in the winter. If there is a moisture problem in the crawl, then some venting in the winter will help, but it doesn't take much.

What else is down there that will be exposed to freezing temps once you isolate the heat to the rooms above? Water lines? Heat ducts? Even drain lines? When I mentioned the perimeter, yes I was intending to cover those 2' concrete walls and seal up any vents. Essentially what you would be doing is bringing the crawl inside the conditioned space. The temp goes up and those floors feel a lot warmer.

I'll let you read as much is covered in that link.

Bud
 
  #5  
Old 11-12-11, 12:37 PM
J
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For some reason I don't think my reply ever posted.

I've read the article, and it makes sense as far as pushing for why you don't insulate the underside of a sub-floor on a vented crawl space, thus freezing everything that was previously being kept warm by the heat transfer above.

If I'm reading your reply correct, you're basically saying I should seal up the entire crawl space to not allow outside air inside. I've read the article here:
To Block... or Not to Block Crawlspace Vents during the Winter? - Planet Green

This says that you shouldn't close off the vents if you have a dirt floor in your crawl space (which I do, it is just covered with poly to crawl around on). It implies that it is code for most homes because you don't want the "breathing" of the house in to let hot air rise and pull in the bad air out of the dirt up into the house. Not sure if that is just an opinion by the article author and many expert now disagree. But I wanted to confirm.

They hit my issue on the head in their "Option 4" in that article. They say to caulk/foam around the upper edges of the perimeter and keep the most obvious leaks from coming in around the molding against the walls. Then to close vents in winter and summer. That makes sense, but still allowing cold air to be right beneath my uninsulated wood floor, which just seems like it will still be cold.

So I wanted to run that by you, are they just being overly cautious on the completely closing off the crawl space and making it a conditioned space thing? Do you recommend that route? Because I agree that I think it might be the best bang for the buck to simply go around the 24" perimeter and insulate it with radiated foam boards or something like that to keep any air from coming in, just afraid of why the builders would have put vents in in the first place if it makes it so inefficient.

Thanks again.

Jeff
 
  #6  
Old 11-12-11, 01:16 PM
B
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A lot has changes in the thinking about how we should be building our homes. The old vent approach was to close them in the winter and open them in the summer. The problem is, summer air is loaded with moisture and inviting that air into a cool crawl space grows mold. Then closing them in the winter wasn't entirely correct as cold winter air is very dry, thus it would eliminate some of the moisture down there. The thinking now is to seal that space, including the ground cover, close or eliminate those vents, insulate and make it part of the conditioned space. Opinions will vary, which leaves people like you making the choice between who you read. For the record, I'm not one of the experts.

I agree your plastic covering should probably be upgraded with careful attention to sealing all seams and up the walls and center posts. Once completed, the air in that space should be very much the same as the rest of the house. It is still a lot of work detailing around the perimeter, but it gives you warmer floors and reduces your heating costs. By the way, a significant portion of the air you currently breathe inside your home is coming from that crawl. As cool air pushes in the lower areas of a house the warmer air is forced up and out the upper areas. In a typical home, all of the air inside exits every couple of hours and is replaced with outside air, mostly from that crawl. Here is another great link on air sealing: http://www.efficiencyvermont.com/ste...ide_062507.pdf

Bud
 
 

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